This invention relates in general to communications systems and, in particular, to satellite communications systems with improved link margin.
Signals in satellite communications systems endure channel effects that often degrade the quality of the signal. Signals which originate from subscriber units (SUs)are especially subject to channel effects, in part because of their limited power output.
Because communications channels experience interference, fading, and blockage, the ability to communicate reliably from an SU to a satellite can change over time. When channels are clear, the signal received at the satellite has a high signal-to-noise ratio (SNR), and the link margin is high. When channels are not clear, the received signal has a lower SNR, and the link margin is low. One simple method of increasing link margin is to increase the power level of the transmitted signal. Increasing power output from SUs can be undesirable, in part because battery life is reduced.
What is needed is a method and apparatus for improving the link margin in communications systems.